A funny biology class

We were in biology class in English, and our teacher is bald. He started asking everyone questions, and then it was one

boy's turn.

"Listen, pick a letter from A–Z."

"Letter C."

"Listen carefully. Do you remember when we talked about shells?"

"Yes, teacher, I remember."

"We said that clams belong to the class Bivalvia. They are soft-bodied aquatic animals protected by two hard shells

that open and close."

"One of their main features is that they do not have a head."

"Yes, teacher, go on."

Then the teacher asked him what a cell is, and the boy answered. After that, the teacher asked:

"Which animal does not have a head?"

"I don't know."

"Listen here, boy. Because of you, either the hair I have left will fall out, or it will grow back."

And we all started laughing.